This invention relates to microstructured films and tapes that have the capability to acquire liquids and to control the directional transport of such liquids for subsequent removal. This transport can be passive or active (i.e., enhanced by an applied potential), and the invention has utility in a number of industrial applications and assemblies.
The collection of liquid in industrial applications (e.g., spills, condensate, ink, pooled fluids, etc.) can cause subsequent problems if the liquid is allowed to remain over a period of time. Some liquid management problems lead to corrosion, power supply loss, excessive weight retention, loss in efficiency, insufficient energy usage, safety hazards, and the like.
Current methods of liquid control focus on the prevention of liquid buildup on a surface through approaches such as absorbent materials, protective films and tapes, and sealants. None of these methods, however, provide for effective liquid removal once liquid is present on a surface.
Transport of liquid across a structured surface may be characterized based upon the mechanism that causes flow of the liquid. Where liquid transport pertains to a non-spontaneous liquid flow regime wherein the liquid flow results, for the most part, from an external force applied to the structured surface, such a liquid transport mechanism is considered xe2x80x9cactivexe2x80x9d. On the other hand, where the liquid transport pertains to a spontaneous flow regime wherein the liquid movement results without the introduction of external forces, such a liquid transport mechanism is considered xe2x80x9cpassivexe2x80x9d.
Active liquid transport products have been developed based upon specific applications, including absorbent pads or a liquid pervious layer combined with liquid transport devices. For example, mat products including active liquid transport and absorbent pads or liquid pervious layers are described in U.S. Pat. No. 5,437,651 to Todd et al. and U.S. Pat. No. 5,349,965 to McCarver. In each case, channels are defined on a surface of a substrate to direct liquid flow from substantially all of the area of a liquid pervious layer. These products remove liquid while having the liquid pervious layer act as a liquid adsorbing and storing layer and/or to define a liquid receiving layer. In Todd et al., a flexible backing plate is attached to an absorbent portion and a suction source is applied to the backing plate. The backing plate comprises a plurality of channels for directing the vacuum provided by the suction source more evenly across the surface of the absorbent portion. In McCarver, a flexible pad or suction rail having a liquid permeable top surface and a liquid impermeable bottom surface is connected to a vacuum source. The suction draws liquid down into a liquid receiving chamber as it passes through the liquid pervious layer, and draws the accumulated liquid away. The liquid receiving chamber contains separation means dividing the chamber into channels for keeping the chamber from collapsing when the chamber is placed under a negative pressure.
Another flexible liquid transport product is commercially available under the trademark xe2x80x9cFluid Controlxe2x80x9d floor suction mat, from Technol Medical Products Inc. This product is used to adsorb fluids that fall from a surgical site during a surgical procedure. The device has an absorbent mat that resides above a multitude of parallel and closed channels. Holes are provided in the channel surfaces that interface with the absorbent mat so that fluid recovered by the mat can be drawn into the channels. The parallel channels are connected to a manifold for attachment with suction tubing. Thus, after fluid has accumulated within the mat, removal thereof can be facilitated through the multiple channels by the application of a vacuum.
A fluid guide device having an open structure surface for attachment to a fluid transport source is described in U.S. Pat. No. 6,080,243 to Insley et al. This reference discloses an open structured surface that defines plural channels and a slot for permitting fluid communication between a distribution manifold and at least a plurality of the channels. A fluid transport source, such as a vacuum generator, is connected to the distribution manifold.
Examples of flexible fluid transport devices that utilize both active and passive fluid transport are described in U.S. Pat. No. 3,520,300 to Flower, U.S. Pat. No. 4,747,166 to Kuntz, and U.S. Pat. No. 5,628,735 to Skow. Examples of other channeled mats for fluid removal are shown in U.S. Pat. No. 4,533,352 to Van Beek et al. and U.S. Pat. No. 4,679,590 to Hergenroeder. Examples of passive fluid transport devices having channeled fluid transport structures are described in U.S. Pat. No. 5,514,120. This reference discloses the use of a liquid management member having a microstructure-bearing hydrophilic surface, preferably in combination with a liquid permeable top sheet, a back sheet, and an absorbent core disposed between the top and back sheets. The liquid management member promotes rapid directional spreading of liquids and is in contact with the absorbent core.
The present invention provides for active and passive transport for liquid acquisition and/or removal in industrial assemblies and applications using microstructured liquid control films.
The liquid control film may be incorporated to transport a liquid to a remote site, to collect a liquid on the film itself, or to disperse the liquid over an increased surface area to promote more rapid evaporation. The microstructured surface has a microstructured topology, and in preferred embodiments is a suitable hydrophilic, polymeric and flexible film. The film properties are described in terms of structure and material.
In one embodiment, the invention is a laminate liquid disposal assembly which includes a liquid control layer and a substrate layer. The liquid control layer has a top side and a bottom side, with the top side having a liquid landing zone for receiving liquid thereon and a liquid removal zone. The top side also has a microstructure-bearing surface with a plurality of channels thereon that facilitate directional flow control of the liquid across the top side from the liquid landing zone to the liquid removal zone. The laminate liquid disposal assembly includes means for attaching the bottom side of the liquid control layer to the substrate layer, and means for removing the liquid from the liquid removal zone on the top side of the liquid control layer.
A porous cap layer may be disposed over the landing zone on the top side of the liquid control layer. Further, the channels on the microstructure-bearing surface have channel ends, and the removing means preferably withdraws the liquid from the channels adjacent one of the channel ends thereof. In another embodiment, the removing means withdraws the liquid from the channels adjacent both channel ends thereof. The removing means may include an absorbent material disposed in communication with the liquid removal zone. The removing means may also include a fluid collection manifold in communication with the channels in the liquid removal zone, and the removing means may further include a vacuum generator in fluid communication with the fluid collection manifold. In one embodiment, the removing means includes a liquid drip collector. In a preferred embodiment, the liquid control layer is a polymeric film, which may include a characteristic altering additive or surface coating. That additive may be selected from the group consisting of flame retardants, hydrophobics, hydrophylics, antimicrobial agents, inorganics, metallic particles, glass fibers, fillers, clays and nanoparticles.
In another embodiment, the invention is a laminate floor assembly which includes a liquid control layer and a floor substrate layer. The liquid control layer has a top side and a bottom side, with the top side having a microstructure-bearing surface with a plurality of channels thereon that facilitate directional flow control of a liquid disposed thereon. The laminate floor assembly includes means for attaching the bottom side of the liquid control layer to the floor substrate layer. A cap layer is also provided, with the cap layer having a top side and a bottom side. The bottom side of the cap layer is placed over the top side of the liquid control layer to define a relatively enclosed channel structure therebetween. The laminate floor assembly includes means for moving liquid along the channel structure defined between the top side of the liquid control layer and the bottom side of the cap layer. Preferably, the cap layer comprises a floor covering, and the floor covering may be selected from the group consisting of carpet, tile, linoleum, wood, concrete, metal or fatigue matting. In one embodiment, the cap layer is porous, and may take the form of a nonwoven material. Preferably, the bottom side of the cap layer is affixed to the top side of the liquid control layer by a pressure sensitive adhesive.
In a preferred embodiment, the moving means creates a pressure gradient along the channel structure. Preferably, the top side of the liquid control layer has at least one cross-channel formed therein to facilitate liquid flow between the channels. A liquid removal aperture is then provided through the liquid control layer in communication with the cross-channel and the moving means. In another preferred embodiment, a plurality of cross-channels are formed in the top side of the liquid control layer to facilitate liquid flow between the channels, and the liquid control layer has a plurality of liquid removal apertures therethrough with each liquid removal aperture being in communication with one of the cross-channels and the moving means. In a preferred embodiment, the channels are defined by generally parallel ridges including a first set of ridges having a first height and a second set of ridges having a second, taller height. An upper portion of each ridge of the second set of ridges may have a lower melting temperature than a lower portion thereof. Preferably, each channel has channels ends and the moving means withdraws the liquid from the channels adjacent one (or both) of the channel ends. In a preferred embodiment, the liquid control layer is a polymeric film, which may include a characteristic altering additive or surface coating. The additive may be selected from the group consisting of flame retardants, hydrophobics, hydrophylics, antimicrobial agents, inorganics, metallic particles, glass fibers, fillers, clays and nanoparticles. The channels have a pattern geometry selected from the group consisting of linear, curve linear, radial, parallel, nonparallel, random, or intersecting.
One embodiment of the present invention is a method of defining an alternative liquid flow path on a polymeric microstructured liquid transport surface of the type having a plurality of channels which are formed to divert a liquid thereon in a first desired directional path and which are formed to control the displacing and evaporating of the liquid disposed on the surface. The method includes forming at least one cross-channel on the polymeric microstructured liquid transport surface to join at least two adjacent channels of the plurality of channels for liquid flow therebetween.
Preferably, the forming step in the inventive method comprises applying heat and/or pressure to the polymeric microstructured fluid transport surface to define the cross-channel thereon. In a preferred embodiment, the channels on a polymeric microstructured liquid transport surface are defined by generally parallel ridges including a first set of ridges having the first height and a second set of ridges having a second, taller height. Preferably, an upper portion of each ridge of the second set has a lower melting temperature than a lower portion thereof, and the forming step includes applying heat to the polymeric microstructured surface along a linear cross-channel segment thereof, to a temperature high enough to melt the upper portions of the ridges of the second set but not high enough to melt the lower portions thereof. Alternatively, the channels are defined by generally parallel ridges with liquid flow valleys therebetween, and the forming step includes cutting away portions of the ridges between adjacent channels. In a preferred embodiment, the polymeric microstructured liquid transport surface defines a top side of a layer having top and bottom opposite sides, and the method of defining an alternative liquid flow path further includes forming a liquid removal aperture through the layer, from top to bottom sides thereof, which is in communication with the cross-channel. The method then can further include urging liquid across the polymeric microstructured liquid transport surface toward the liquid removal aperture, and may yet further include coupling the liquid removal aperture to a liquid collection receptacle. In a preferred embodiment, the inventive method also includes adhering a cap layer (which could be porous) onto the polymeric microstructured liquid transport surface.
In another embodiment of the present invention, the invention is defined as a method for enhancing the rate of evaporation of liquid disposed on a surface which includes defining an exposed face of a film as a polymeric microstructure-bearing surface with a plurality of channels thereon, where the channels are defined by generally spaced apart projections with valleys therebetween. The method includes introducing a liquid onto the polymeric microstructure-bearing surface of the film, wherein the channels are formed to facilitate spontaneous wicking of the liquid along each channel which receives liquid therein so that the exposed evaporative active surface of the liquid is increased by its spatial distribution in the x-direction along the valley of each channel, its spatial distribution in the y-direction between the projections of each channel, as well as by forming meniscus height variations of the liquid in each channel in the z-direction. The method further includes exposing the increased evaporatively active surface area of the liquid on the microstructure-bearing surface to ambient air.
In a preferred embodiment, the inventive method includes exposing the liquid disposed on the microstructure-bearing surface to a moving air stream. Preferably, the inventive method further includes introducing a sufficient quantity of liquid onto the polymeric microstructure-bearing surface to define a continuous flow of liquid over the surface. Further, the inventive method may include collecting non-evaporative liquid that has flowed over the surface, and after further processing of the liquid, recirculating the liquid collected from the surface for reintroduction thereon. In a preferred embodiment, the method includes exposing at least a portion of the liquid flowing over the surface to a moving air stream, which may be moving in the generally opposite direction to the liquid flow direction across the surface. Alternatively, the air stream may be moving in a direction generally perpendicular to the direction that the liquid is flowing across the surface.
In alternate embodiments, the projections are ridges and/or may be discontinuous along the channels. In one embodiment, the polymeric microstructure-bearing surface has first and second ends, and the inventive method includes introducing the sufficient quantity of liquid onto the surface adjacent the first end thereof, and aligning the surface so that its first end is higher than its second end (e.g., the exposed face may be aligned on a generally vertical plane). The inventive method may further include defining additional surface texture features on the polymeric microstructure-bearing surface in order to increase the surface area thereon for supporting the liquid. In one preferred embodiment, the polymeric microstructure-bearing surface has generally parallel channels extending between first and second ends thereof, and the inventive method further includes aligning the surface so that one end of the channels is higher than the other end. Alternatively, the microstructure-bearing surface may be aligned so that an intermediate portion thereof is lower than its first and second ends. In a preferred embodiment, the inventive method further includes providing an additive in the polymeric microstructure-bearing surface, wherein the additive is selected from the group consisting of flame retardants, hydrophobics, hydrophylics, antimicrobial agents, inorganics, metallic particles, glass fibers, fillers, clays and nanoparticles.